A month before the May 21 runoff, likely voters favored the councilman over the city controller by 50% to 40%. Perhaps most worrisome for Greuel: her failure so far to establish a base in the Valley.

Eric Garcetti has opened a commanding 10-point lead in the Los Angeles mayor's race over rival Wendy Greuel, whose dogged fight to win the backing of public employee unions appears to be undercutting her on her home turf in the San Fernando Valley, according to a new USC Price/Los Angeles Times poll.

A month before the May 21 runoff, likely voters favored Garcetti over Greuel by 50% to 40%.

The survey also found no sign of success for Greuel's effort to gain an edge among women by highlighting her potential to make history as the city's first female mayor. Women preferred Garcetti, 50% to 41%.

Latinos and younger voters backed Garcetti by still wider margins. The city councilman from Silver Lake has strengthened his standing in the central city and Eastside neighborhoods that he won decisively in the March primary. He has also built a solid lead on the Westside — a key target of Greuel's.

Perhaps most worrisome for Greuel, the city controller, is her failure so far to establish a base in the Valley, where the two are effectively tied. Greuel, who lives in Studio City, had hoped that audits by her office that found wasteful spending of taxpayer money would appeal to the Valley's Republicans, often a pivotal vote in L.A. elections.

Instead, Garcetti has emerged with a lopsided lead among conservatives citywide, picking up support from many of those who voted in the primary for Republican radio personality Kevin James, now a Garcetti backer.

Greuel's tepid support in the Valley, which she represented on the City Council from 2002 to 2009, poses a major challenge for her in the closing weeks of the race. Though Democrats dominate the Valley, many of the city's Republicans live on its western and northern ends.

"That's an untenable situation for Greuel," said Dan Schnur, director of the USC Sol Price School of Public Policy/Los Angeles Times City Election Poll.

Still, even as election officials prepare for the start of mail-in voting on Monday, the contest remains highly fluid, with millions of dollars in TV and radio ads still ahead.

And Greuel holds some clear advantages.

Voters trust Greuel to handle schools better than her opponent would.

"I've got kids in school, and I think she'd do more in terms of improving LAUSD," poll respondent Chris Eisenberg of Sherman Oaks said in a follow-up interview, alluding to the L.A. Unified School District. Greuel often tells voters that her son attends a public elementary school.

A plurality of the voters surveyed also chose Greuel as the candidate who seems genuine and says what she really believes. They picked Garcetti as the one who seems like a typical politician and says things just to get elected.

A plurality also chose Garcetti as the one who cares more about big businesses and developers than Los Angeles as a whole. Greuel has tried to stoke further doubts about Garcetti's integrity. On Friday, after polling concluded, she started airing a TV ad attacking his personal investments.

Also working in Greuel's favor is her endorsement by Bill Clinton, with whom she campaigned on Saturday at Langer's Deli near MacArthur Park. The poll found a majority of voters was more likely to support a candidate backed by the former president. Another of Greuel's TV ads spotlights her work on disaster relief in the Clinton administration after the 1994 Northridge earthquake.

"People like Bill Clinton, and people like people who are liked by Bill Clinton," said pollster Chris St. Hilaire of M4 Strategies, the Republican half of the bipartisan team that conducted the survey.

The poll also suggested that African Americans — a key group up for grabs — were tilting toward Greuel. But the poll's sample size was too small to draw firm conclusions about African Americans, Asians and other groups that can swing a close race.

The telephone survey of 500 likely voters, taken Monday through Wednesday, had a margin of sampling error of 4.4 percentage points in either direction, with wider margins for subgroups.

For Garcetti, the poll offered an abundance of good signs. Likely voters gave him higher marks than Greuel on how he would handle traffic, mass transit, jobs, crime and public safety, always areas of concern for city voters. The results suggested minimal returns so far for one of Greuel's thrusts: She has vowed to hire about 2,000 new police officers and 700 new firefighters and paramedics and also attacked Garcetti for Fire Department budget cuts.

A plurality of likely voters also chose Garcetti when asked which candidate could make the tough decisions necessary to move the city in the right direction, which would represent every neighborhood and race in L.A., and which had a strong and clear vision for the city's future.